Whether your computer will be used on a desk or a lap, the same minimum specifications apply:

You need at least 256 megabytes of memory, at least 40 gigabytes of hard drive, a CD-RW drive and LCD monitor (which, beyond looking cool, will take up less space, won't flicker and will use less electricity than an old-fashioned cathode-ray tube). On a desktop, add a 64-meg video card; on a laptop, add a WiFi receiver.

When in doubt, a machine with more USB 2.0 ports is better than one with fewer, especially if at least two of them are on the front or some other spot more convenient to reach than the back of a desktop PC's case.

Note that I didn't list processor speed -- precisely because the slowest hardware you can find today is still more than fast enough for any ordinary home use.

Here's where you should think of spending money on upgrades: Double the memory if you want to get into digital photography or simply tend to run a lot of applications at once. Up the hard drive to 60 gigabytes if you're going to plug a digital camera into the thing, and go up to 80 if you plan on building an MP3 collection.

Thinking of editing video? Then you can start to think about the processor again -- spend more to get more speed. You'll also need a 100-gig hard drive and a FireWire port to plug a digital camcorder into, plus a DVD burner -- preferably DVD+RW. If you're into games, a 128-megabyte video card and a surround-sound sound card can be worthwhile investments.